I am 6ft / 180cm and went with XL and it feels perfect.
My last e-MTB was Rocky Mountain altitude powerplay in Large and always felt a bit cramped to me. I did have heaps of issues with having extremely sore bum from the saddle on the RM and tried 4 different saddles, change angles etc, with the same issue. Last saddle was the Ergon e-MTB specific saddle and still had heaps of issues with pain for days after a ride.
Interestingly i have this same Ergon e-MTB saddle on the Amflow XL and have not had any issues with saddle soreness! So good, love the Amflow.